Abstract Gestational and early postnatal adverse experiences, because of their psychopathological consequences later in life, represent a significant burden for the affected individual and society. We identified an epigenetic motif at two thousand genomic regions in neurons that, via dynamic switching between methylated and unmethylated states, may control gene expression. The stochastic balance between the two states is altered by early life adversity in a subpopulation of neurons, resulting in abnormal neuronal functioning. We will test the hypothesis that permanent changes in the methylation state of key ?switches? in the adversity-activated neurons represent the ?cellular memory? of early life adverse experiences. Adversity-induced epigenetic changes increase the excitability of neurons, making them permanently eligible for recruitment during behavioral tasks. This in turn, increases the responsiveness of the circuit to novel/stressful stimuli, manifested as exaggerated fear reaction/anxiety later in life. Besides of the theoretical implications (coding environmental effects via binary epigenetic switches), our work has translational significance. The sensitivity of DNA methylation based switches (due to their metastability), compared to the rest of the epigenetically more stable genome, provides an opportunity for their selective manipulation to mitigate the adverse effects of ELA.